1. Field of the Invention
The present invention relates generally to a vehicle transmission. More specifically, the present invention relates to a vehicle transmission that is known as a twin-clutch transmission.
2. Background Information
Some conventional transmissions are provided with two drive transmission paths using a pair of discrete clutches that selectively input an engine rotation into the drive transmission paths. One example of this type of conventional transmission is described in Japanese Patent Application Laid-Open Publication No. 2003-120764A (Cf., FIGS. 17 to 25). This type of transmissions is called a twin-clutch transmission, which can be shifted without interruption of a driving force transmission by alternately engaging these two clutches. The twin-clutch transmissions have high efficiency as compared to automatic transmissions that include a torque converter. Thus, twin-clutch transmissions are increasingly expected to be used in automobiles for substantial fuel consumption savings.
Basically, with the twin-clutch transmission described in this publication, the number of tooth engagements or sets of engaged paired gears for torque transfer is “3” for the first gear, the number of tooth engagements or sets of engaged paired gears for torque transfer is “1” for the second gear, the number of tooth engagements or sets of engaged paired gears for torque transfer is “1” for the third gear, the number of tooth engagements or engaged gear pairs for torque transfer is “3” for the fourth gear, the number of tooth engagements or se sets of engaged paired gears for torque transfer is “3” for the fifth gear, the number of tooth engagements or sets of engaged paired gears for torque transfer is “1” for the sixth gear, the number of tooth engagement for torque transfer is “1” for the seventh gear, the number of tooth engagements or sets of engaged paired gears for torque transfer is “3” for the eighth gear, and the number of tooth engagements or sets of engaged paired gears for torque transfer is “4” for the reverse gear.
In this publication, a first reduction gear pair is used for the first gear, fourth gear, fifth gear, eighth gear and reverse gear, but the direction of power transfer through the first reduction gear for the first gear and fifth gear and the direction of power transfer for the fourth gear, eighth gear and reverse gear are the opposite to each other. The direction of power transfer in the former case is as follows: “from the first input shaft to the first reduction gear pair to the sub shaft”, and the direction of power transfer in the latter case is the opposite direction as follows: “the sub shaft to the first reduction gear pair to the first input shaft”. On this account, when a reduction ratio of the first reduction pair is “r” for the first gear, it becomes “−1/r” for the reverse gear. Thus, the first reduction pair is being increased in speed for the first gear and it is being reduced in speed for the reverse gear.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved vehicle transmission. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.